Free wheeling 2-speed motor wheel

ABSTRACT

A motor wheel for use in a ground engaging drive wheel of a vehicle includes a hydraulic motor disposed in a housing, the output shaft of the motor is connectable through a complex planetary gearing and clutch arrangement to drive a casing which is rotatably mounted relative to the housing. The driving force from the output shaft of the hydraulic motor is transmitted to a planetary gear set by means of an arcuately configured sun gear formed on one end of the drive shaft, the planetary gears are disposed about the sun gear to transmit the driving force to a ring gear mounted in the casing. A planetary carrier is disposed in the casing for supporting the planetary gears during relative rotative movement about the sun gear. The planetary carrier is normally disposed in an initial neutral position for free rotative motion relative to both the casing and the housing to thereby provide free wheeling of the motor wheel. The planetary carrier is axially slidable relative to the sun gear and ring gears in either direction from the neutral position to thereby provide a high speed and a low speed gear ratios. Driving engagement between the carrier and the housing is established upon movement of the carrier in one direction from the neutral position and driving engagement between the carrier and the casing is established upon movement of the carrier axially in the other direction from the neutral position. Springs are provided to maintain the carrier normally centered and out of engagement with either the casing or the housing to provide the free wheeling condition of said wheel motor. Hydraulically actuated annularly shaped clutch pistons are disposed in recesses in the casing and housing respectively and are operable upon the application of fluid pressure thereto to move the carrier into driving engagement with either the housing or the casing to thereby provide a hydraulically operated motor wheel having both direct and low speed driving ratios as well as free wheeling. Valve means are provided to part pressurized hydraulic fluid for actuating the pistons and to simultaneously reverse fluid flow through the hydraulic motor upon actuation thereof to provide the required direction of rotation of the hydraulic motor.

United States Patent 1 Vegners NOV. 6, 1973 [21] Appl. No.: 236,416

[52] US. Cl 180/66 F, 74/792, 180/43 B [51] Int. Cl B60k 7/00 [58] Fieldof Search 180/66 F, 44 F, 44 M,

[56] References Cited UNITED STATES PATENTS 3,184,994 5/1965 Stahl180/43 B X 3,251,243 5/1966 Kress 74/792 X 2,588,187 3/1952 Weiser74/812 X 2,738,849 3/1956 Nubung 180/66 R 2,591,363 4/1952 Kraft et al74/791 X 2,935,901 5/1960 Petronovich... 74/792 3,458,005 7/1969 Malm etal..... 180/43 B X 2,939,344 6/1960 Harris 180/43 B 3,422,917 l/l969Guinot 180/44 F 3,272,279 9/1966 Budzich 180/44 M PrimaryExaminer-Kenneth H. Betts Assistant ExaminerDavid M. MitchellAttorney-Thomas E. Davis 57 ABSTRACT A motor wheel for use in a groundengaging'drive wheel of a vehicle includes a hydraulic motor disposed ina housing, the output shaft of the motor is connectable through acomplex planetary gearing and clutch arrangement to drive a casingwhichis rotatably mounted relative to the housing. The driving force from theoutput shaft of the hydraulic motor is transmitted to a planetary gearset by means of an arcuately configured sun gear formed on one end ofthe drive shaft, the planetary gears are disposed about the sun gear totransmit the driving force to a ring gear mounted in the casing. Aplanetary carrier is disposed in the casing for supporting the planetarygears during relative rotative movement about the sun gear. The

planetary carrier is normally disposed in an initial neutral positionfor free rotative motion relative to both the casing and the housing tothereby provide free wheeling of the motor wheel. The planetary carrieris axially slidable relative to the sun gear and ring gears in eitherdirection from the neutral position to thereby provide a high speed anda low speed gear ratios. Driving engagement between the carrier and thehousing is established upon movement of the carrier in one directionfrom the neutral position and driving engagement between the carrier andthe casing is established upon movement of the carrier axially in theother direction from the neutral position. Springs are provided tomaintain the carrier normally centered and out of engagement with eitherthe casing or the housing to provide the free wheeling condition of saidwheel motor. Hydraulically actuated annularly shaped clutch pistons aredisposed in recesses in the casing and housing respectively and areoperable upon the application of fluid pressure thereto to move thecarrier into driving engagement with either the housing or the casing tothereby provide a hydraulically operated motor wheel having both directand low speed driving ratios as well as free wheeling. Valve means areprovided to part pressurized hydraulic fluid for actuating the pistonsand to simultaneously reverse fluid flow through the hydraulic motorupon actuation thereof to provide the required direction of rotation ofthe hydraulic motor.

11 Claims, 7 Drawing Figures PAIENTEDnuv 6197a 3770.07 SHEET 1 [1F 3SHEET 38F 3 PAIENTEmmv 519?;

HIGH SPEED Low SPEED TO 22 TO 24 1 FREE WHEELING Z-SPEED MOTOR WHEELBACKGROUND OF THE INVENTION This invention relates generally to ahydraulically actuated motor wheel and control system for a groundengaging wheel of a vehicle. More specifically, this invention relatesto a hydraulically actuated motor wheel having a planetary gear set andcontrol system therefore and wherein selectively actuatablehydraulically operated clutches are provided to lock the carrier of theplanetarygear set to either a stationary housing or a rotatable casingto provide a plurality of speed ratios in a motor wheel of the type towhich this invention relates.

I-lydraulically driven motor wheels are known in the art. Morespecifically, hydraulically driven motor wheels having a planetary gearset and a single hydraulically actuated clutch are also known in theart. One disadvantage of this type of system was that the motor wheelwas only capable of providing either free wheeling or one set driveratio. Thus, prior art motor wheels of the type to which this inventionrelates could not provide a sufficient range of both mechanicaladvantages in the form of output torque and high rotational speeds tocover a wide range of operating conditions. The most pertinent exampleof this type of prior art known to the applicant is US. Pat. No.3,458.005 issued July 29, I969 to DJ. Malm et al.

Further, hydraulically actuated motor wheels having change speed gearingand variable ratio hydraulic motors are also known in the art. Examplesof these devices are shown in US. Pat. Nos. 3,270,826 issued Sept. 6,1966 to Middlesworth et al., 3,469,646 issued Sept. 30, 1969 to OConnorand 3,391,753 issued July 9, 1968 to Anderson.

However, to date no one has provided a hydraulically actuated motorwheel having planetary gearingand including a plurality of hydraulicallyactuated clutches and wherein a normal unactuated position the carrierof the planetary gear set is freely rotatable to provide a free wheelingfeature to the wheel motor and wherein the carrier of the planetary gearset is axially slidable into clutching engagement with either astationary or rotating portion of the motor wheel to provide a pluralityof speed ratios therein.

SUMMARY OF THE INVENTION According to the present invention, an improvedhydraulically actuated wheel motor drive system is provided for use on avehicle and wherein the wheel motor is operable to provide a pluralityof output speed ratios by means of selectively actuatable clutches whichlock the carrier of the planetary gear set to either a stationary orrotating portion of the motor wheel.

The motor wheel includes a geroter type hydrauliv cally actuated fluidmotor. The fluid motor operating mechanism includes an internallytoothed ring member and an externally toothed star member disposedeccentrically within the ring member for rotational and orbital movementthereto. The teeth of the members intermesh to form expanding andcontracting fluid chambers upon relative orbital and rotational movementtherebetween. Valve means are drivingly connected to the internallytoothed star member whereby hydraulic fluid under pressure may beadmitted to or exhausted from the expanding and contracting chambers insynchronism with either orbiting or rotating movement of the starmember. The fluidmotor is disposed within a housing of the motor wheelwhich is adapted to be mounted on a vehicle. The motor wheel furtherincludes a casing rotatably disposed relative to the housing and aplanetary gear set. Disposed within the casing is a floating drive shafthaving one end dr'ivingly'connected to the star member of the fluidmotor. The other end of the drive shaft is configured to provide a sungear for the planetary gear set. Planetary gears are provided totransmit driving rotation between the sun gear and a ring gear disposedin the housing. The planetary gears are rotatably supported relative toa planetary gear carrier in the casing. The planetary gear carrier isaxially slidable within the casing in either direction from an initialneutral position. The planetary carrier includes a first clutch surfaceadapted to engage a corresponding clutch surface on the housing uponaxial movement of the carrier in one direction from the initial neutralposition and a second clutch surface adapted to engage a correspondingclutch surface on the casing upon axial movement of the carrier in theother direction from the initial neutral position. Springs are providedon either side of the carrier to maintain the carrier in the initialneutral position. Clutch actuating pistons are provided on either sideof the carrier to enable the carrier to be selectively moved intoclutching engagement with either the housing or the casing by selectiveapplication of fluid pressure behind the pistons.

Because grounding of the carrier to the housing as opposed to groundingit to the casing would result in reversing the direction of rotation ofthe drive wheel,

valve means and hydraulic system are provided-to automatically andsimultaneously reverse the direction of fluid flow through the motordepending on which clutch actuating piston is being pressurized.

One feature of this arrangement'is that it provides an extremely compactmotor Wheel which may be used in vehicle wheels of any type and whereinthe motor wheel is operable to provide a plurality of output gear ratioswhile maintaining the compact design.

Another object of this invention is to provide a hydraulically actuatedmotor wheel wherein a planetary carrier of a planetary gear set isaxially slidable under the influence of hydraulic pressure to provide aplurality of output speed ratios.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows the motor wheel andcontrol system of the present application disposed in a vehicle.

FIG. 2 is a cross sectional view taken axially along the center line ofthe motor wheel of the present invention showing the internalconstruction thereof.

FIG. 3 is a sectional view taken along the line 3-3 I of FIG. 2 showingfurther details of the motor wheel of DESCRlPTION OF THE PREFERREDEMBODIMENT With reference to FIG. 1 there is shown a vehicle having amotor wheel 12 disposed within the hub of a ground engaging drive wheelof the vehicle 10.

With reference to FIG. 2, the motor wheel 12 includes a housing 14adapted to be mounted on the vehicle 10 and a casing 16 adapted to bemounted as the hub of a ground engaging vehicle drive wheel 13. Thecasing 16 is rotatably mounted relative to the housing 14 by means of apair of large tapered roller bearings 18 and 20 disposed therebetween.The housing 14 is adapted to be connected to a variable displacementhydraulic pump (not shown) disposed on the vehicle by means of an inletport 22 and an outlet port 24. The inlet port 22 and outlet port 24 maybe reversed in function depending upon the desired direction of rotationof the motor wheel 12. The-housing 14 is further provided with a one oilpassage 26 and another separate oil passage 28. The oil passages 26, and28 may be selectively pressurized by means of a two way open centerhydraulic valve 29 disposed on the vehicle which is connected to ahydraulic pump (not shown). Another open center two way hydraulic valve29a is provided to reverse direction of flow to ports 22 and 24. Linkpin 29b connects the valve control handles for simultaneous operation.The purpose of the selectively pressurizable passages 26 and 28 andvalves 29 and 29a will become more apparent from the description whichfollows hereinafter. For ease of manufacture, the housing 14 iscomprised of a plurality of bolted-together sections 14a, 14b and 14c.The casing 16 islikewise comprised of a plurality of bolted togethersections 16a, 16b and 16c.

As shown in FIG. 2, a plurality of O ring or quad ring type seals one ofwhich is generally designated are incorporated to prevent leakagebetween various surfaces within the motor wheel 12 as will be evident tothose skilled in the art.

Disposed within the housing 14 is a geroter type hydraulic motor 30. Thegeroter type motor is particularly advantageous for this applicationsince this type'of motor is substantially instantaneously reversible.The hydraulic motor 30 includes an internally toothed ring member 32 andan externally toothed star member 34 eccentrically disposed forrotational and orbital movement relative to the ring member. The teethof these members intermesh to provide expanding and contracting fluidchambers upon relative orbital and rotational movement therebetween. Avalve member 36 is provided in the housing and is connected to be drivenin synchronism with either rotational movement of the externally toothedmember by valve drive means 38. The valve member 36, thus is effectiveto sequentially connect the expanding and contracting chambers to theinlet port 22 and outlet port 24 thereby controlling fluid flow throughthe expanding and contracting chambers in synchronism with the movementof the externally toothed member.

A hydraulic motor of similar design 'and suitable for performing thefunction previously set forth is more fully disclosed and described inU.S. Pat. No. 3,572,983 issued to McDermott and assigned to the assignee of the present invention. The specification of that applicationis hereby incorporated by reference into this application.

A free floating drive shaft or dog-bone shaped member 40 is provided totransmit the driving orbital and rotary movement of externally toothedmember 34 into useful output rotary torque for the wheel motor 12. Thedrive shaft 40 is configured with arcuately shaped spline 42 andarcuately hobbed gear teeth 44 respectively on the ends thereof. Athrust block 46 is provided to prevent axial movement of the drive shaftmember 40. The arcuate splines or gear teeth on either end of the driveshaft 40 are necessary in order to transmit the rotary-orbital typemotion of the externally toothed member 34 into the purerotative torqueeffort necessary for operation of the wheel motor. It should beemphasized that the use of a free floating drive shaft member 40 in adevice of this type is particularly advantageous because of theextremely high torque loads which must be transmitted. Since the shaft40 is free floating, it may be permitted to seek its own center and thusmore effectively transmit the torque load.

The wheel motor 12 is provided with a planetary gear set 50 wherein thearcuately toothed end 44 of shaft 40 may be considered a sun gear. Theplanetary gear set further includes a plurality of planet gears 54rotatably disposed on planet gear shafts 56 which are in turn mounted ina planet carrier 58. The plane gears 54 are effective to transmitdriving rotation between the sun gear or splined end 44 of shaft 40 anda ring gear 60 formed about the interior peripheral surface of section16b of casing 16. The planet gear carrier 58 and associated planet gears54 are slidably mounted for axial movement relative to the sun gear 44and ring gear 60. The carrier 58 is further provided with a one clutchsurface 62 and another clutch surface 64 disposed thereon. The clutchsurface 62 is confronted by a corresponding clutch surface 66 on thehousing and normally axially spaced therefrom. The clutch surface 64 ofthe carrier 58 is likewise confronted with a correthe carrier 58 to bemoved axially to engage the clutch surface 62 of the carrier with thecorresponding clutch surface 66 of the housing to thereby preventrelative rotation between the carrier and the housing. The clutchactuating means 70 includes a fluid supply passage 72 associated withselectively pressurizable passage 26 of the housing and an annularring-shaped actuating shoe 74 received in a ring-shaped recess of thecasing. Shoe 74 is advantageously provided with pressure balancinggrooves 744 which are provided to prevent metal to metal contact betweenthe shoe 74 and carrier 58. This surface is supplied with pressurizedhydraulic fluid by means of holes 74b therein. Springs 76 and stake pins78 are provided to prevent relative rotational movement between theactuating shoe 74 and the casing 16.

Another clutch actuating means 80 which is essentially identical to theclutch actuating means 70 is provided on the other side of the carrierand acts between the carrier and the housing. The clutch actuating means80 comprises a fluid supply passage 82 (shown in phantom out of positionin FIG. 2 for clarity) associated with selectively pressurizable passage28 of the housing 14. An annularly shaped actuating shoe 84 is providedin a ring-shaped recess of the housing 14 to enable the carrier 58 to beselectively axially moved whereby clutching surface 64 of the carrier 58may be brought into driving engagement with clutching surface 68 of thecasing 16 to thereby prevent relative rotary movement between the casingand the carrier. Pressure balancing grooves 84a and supply passages 84bare likewise provided in shoe 84. Springs 86 and stake pins 88 arelikewise provided to prevent relative rotary motion between the housing14 and annular shoe 84. The springs 76 and 86 are likewise effective tomaintain the carrier in a normally centered or neutral position tothereby enable free wheeling of the wheel motor 12 when neither of thepassages 26 or 28 of the housing are pressurized by movement of thehydraulic valve 29 on the vehicle 10.

Additionally, flange 90 of casing 14 having a plurality of mountingholes 14d therein is advantageously provided for mounting of adisc typebrake mechanism (not shown) to retard motion of the vehicle uponapplication thereof.

Additionally or alternatively, additional clutch means could be providedto lock other portions of the planetary gear set relative to either thecasing or the housing to provide additional or alternative drivingratios.

DESCRIPTION OF OPERATION When the operator of a vehicle desires to drivethe vehicle, he must decide whether a very high starting torque isrequired as in starting on an uphill grade or with a very heavy load. Ifthis is the case he would operate control valve 29 and simultaneouslycontrol valve 29a on the vehicle to pressurize passages 24 and 26thereby creating fluid pressure in passage 72 and behind clutchactuating shoe 74. This pressure behind clutch actuating shoe 74 wouldcasue axial movement 6 gear 60 rotates in the opposite direction fromthe sun gear 44.

When the vehicle reaches sufficient speed, the operator moves thecontrol handle attached to valves 29 and 29a across neutral to theopposite position thereby pressurizing ports 22 and 28 and passage 82associated with port 28 while simultaneously relieving pressure fromports 24 and 26 and passage 72 associated with port 26. This reversesdirection of rotation of the hydraulic motor 30. Pressure behind shoe 84moves carrier 58 to the left as shown in FIG. 2 to provide drivingengagement between surface 64 of the carrier 58 and surface 68 of thecasing. In this position the carrier 58 is locked for rotation with thecasing 16. Since the carrier 58 now rotates with the ring gear 60, adirect or 1 1 gear ratio is provided. In other words, relative rotationbetween the sun gear 44 and the ring gear 60 is prevented in this clutchposition. The casing 16 thus rotates directly with the sun gear 44, theplanet gears 54 act merely as fixed members to transmit .the torque.Thering gear 60 rotates in the same direction as the sun gear 44.

When it is desired to operate the motor wheel 12 to drive the vehicleinthe reverse direction, the operator merely reverses the output flowfrom the variable dis placement pump (not shown) on the vehicle as iswell I known in the art. Operation of the high speed and low of theplanetary carrier 58 to provide clutching engagement between surface 62of the carrier and'clutch surface 66 of the housing 14. Thus whenpassages 24 and 26 are pressurized, the motor wheel would supply a lowspeed-high torque forward rotation output. The flow of the pressurizedhydraulic fluid from valve 29a would enter the housing at port 24 andleave the'housing through port 22. After entering the housing, thehydraulic pressurized fluid would pass through the valve means 36 andinto the expanding chambersbetween the internally toothed member 32 andthe externally toothed member 34 thereby causing rotational and orbitalmotion of the externally toothed member. As the chamber contracts,hydraulic fluid will flow back out through the valve means to port 22,and return to the pump. Rotational and orbital motion of the externallytoothed member 34 would cause rotation of drive member 40. The rotationof drive member 40 would be transmitted through the sun gear 44 at oneend thereof to the planetary gears 54 which would in turn rotatev aboutthe planet gear shafts 56 thereby driving ring gear 60 and casing 16 ata predetermined ratio, for example 4:1. This is because the carrier 58is lockedto the housing 14 and thus the planet gear shafts 56 arelikewise stationary relative to the housing. Torque is transmitted fromthe sun gear 44, to planetary gears 58 then directly to ring gear 60. Inthis position, the ring speed control valves 29 and 29a remains the sameas previously described. Thus direction of vehicle movement iscontrolled in a standard manner well known in the art.

If the operator desires to allow the vehicle to coast, he merely movesthe handle attached to control valves 29 and 29a to the neutralposition. When this happens, the springs 76 and 86 will center thecarrier and the motor wheel will be in a free wheeling position. Thisfeature is particularly advantageous for towing large constructionvehicles at highway speeds and eliminates the need for a special trailerfor this type of vehicle.

' I claim:

1. A hydraulic motorized wheel for use as 'a drive wheel of a vehicle,said motorized wheel comprising a housing adapted to be mounted on avehicle,

a casing rotatably mounted relative to said housing,

a hydraulically operated motor mounted on said housing having arotatable drive shaft extending into said casing,

a planetary gear set in said casing, the sun gear of said planetary gearset being driven by said drive shaft, said planetary gear set furtherincluding a planetary gear disposed in driving engagement with said sungear, a planetary gear carrier mounted in said casing for relativesliding movement in either direction from a neutral-position, saidplanetary carrier being freely rotatable relative to both said casingand said housing when in said neutral position, and a ring gear mountedin said casing in driving engagement with said planetary gear,

first clutch means in said motorized wheel operable upon actuationthereof to move said planetary carrier in one direction from saidneutral position to prevent relative rotation between said housing andsaid planetary carrier and to provide a first drive ratio, and

second clutch means in said motorized wheel operable upon actuationthereof to move said planetary carrier in the other direction from saidneutral position to prevent relative rotation between said casing andsaid planetary carrier to provide a second drive ratio.

2. The invention of claim 1 wherein said first and second clutch meansare selectively actuatable by hydraulic pressure, and valve means influid communication with said hydraulic motor and both of said clutchmeans, said valve means being operable to reverse the direction ofoperating fluid flow to said hydraulic motor simultaneously withactuation of said second clutch means after actuation of said firstclutch means to reverse rotation of said output shaft simultaneouslywith actuation of said second clutch means.

3. The invention of claim 1 wherein said hydraulic mctor includes anexternally toothed member, an internally toothed member, and motor valvemeans, said externally toothed member being operably associated withsaid drive shaft and eccentrically disposed relative to said internallytoothed member for rotational and orbital movement relative to an axisthereof, the teeth of said members intermeshing to define expanding andcontracting fluid chambers upon relative rotational and orbital movementtherebetween, said motor valve means being connected to admit andexhaust fluid from said chambers in synchronism .with one of themovements of said externally toothed member.

4. The invention of claim 3 wherein the drive shaft of said hydraulicmotor includes splined portions thereon, and said externally toothedmember has a splined bore therein, one of said splined portions of saiddrive shaft being drivingly received in the splined bore of saidexternally toothed member, another of said splined portions being thesun gear for said planetary gear set.

5. A hydraulic motorized wheel for use as a drive wheel vehicle, saidmotorized wheelcomprising a housing adapted to be mounted on a vehicle,

a casing rotatably mounted relative to said housing,

a hydraulically operated motor mounted on said housing having arotatable drive shaft extending into said casing,

a planetary gear set in said casing, the sun gear of said planetary gearset being driven by said drive shaft, said planetary gear set furtherincluding a planetary gear disposed in driving engagement with said sungear, a planetary gear carrier mounted in said casing for normally freerotation relative to both said casing and said housing, and a ring gearmounted in said casing in driving engagement with said planetary gear,said planetary gear carrier being axially slidable relative to said ringand sun gear in either direction from an initial neutral position wheresaid planetary carrier is freely rotatable relative to both said casingand said housing,

first clutch means in said motorized wheel operable upon actuationthereof to prevent relative rotation between said housing and saidplanetary carrier and to provide a first drive ratio, said first clutchvmeans including pressure actuatable means for moving said carrier inone direction from said neutral position,

second clutch means in said motorized wheel operable upon actuationthereof to prevent relative rotation between said casing and saidplanetary carrier to provide a second drive ratio, said second clutchmeans including pressure actuatable means for moving said carrier in theother direction from said initial neutral position, and

means normally biasing said carrier toward said initial neutralposition.

6. T he invention of claim 5 wherein said first and second clutch meanscomprise first and second clutching surfaces on said carrier andcorresponding adjacent clutching surfaces on said housing and saidcasing respectively.

7. The invention of claim 6 wherein a first element of clutch frictionalmaterial is disposed between the first clutching surface on said carrierand the corresponding surface on said housing, and a second element ofclutch frictional material is disposed between the second clutchingsurface on said carrier and the corresponding surface on said casing.

8. The invention of claim 7 wherein said first clutch means includes afirst piston received in a recess in said casing, said first pistonhaving a bearing surface disposed for abutting engagement with a bearingsurface of said carrier, said second clutch means including a secondpiston received in a recess in said housing, said second piston having abearing surface disposed for abutting engagement with a bearing surfaceof said carrier, and wherein the biasing means for normally biasing saidcarrier toward said initial neutral position comprise biasing meansacting between said casing and said first piston and said housing andsaid second piston to constantly urge said surfaces toward abuttingengagement and to thereby urge said carrier toward the initial neutralposition.

9. The invention of claim 5 wherein said first and second pressureactuatable means comprise annular pistons received in recesses in saidcasing and said housing respectively on opposite sides of said carrierand selectively pressurizable passage means in said casing and saidhousing communicating with said recesses.

ll). The invention of claim 9 wherein said means normally biasing saidcarrier toward said initial neutral position comprise springs actingbetween the casing and its associated piston and the housing and itsassociated piston thereby biasing said pistons into engagement with saidcarrier and thereby biasing said carrier toward said initial neutralposition.

11. A hydraulic motorized wheel for use in a vehicle, said motorizedwheel comprising a housing adapted to be mounted on a vehicle, a casingmounted on said housing for rotation relative thereto, a reversiblerotary hydraulic motor disposed on said housing and having rotatableoutput shaft extending into said casing, a planetary gear set disposedin said casing, said planetary gear set including a sun gear, planetarygears, planetary gear carrier means and a ring gear, the sun gear ofsaid planetary gear set being drivingly connected for rotation with theoutput shaft of said hydraulic motor, first clutch means operable uponactuation thereof to prevent rotation of said casing relative to saidsun gear to thereby provide a first drive ratio between said outputshaft and said casing, second clutch means operable upon actuationthereof to prevent rotation of another portion of said planetary gearset relative to said housing to thereby provide a second driving ratiobetween said output shaft and said casing, a first valve in fluidcommunication with said motorized wheel, said first valve being operableto selectively actuate said first and second clutch means, and a secondvalve in fluid communication with said motorized wheel, said secondvalve being operable to control the direction of operating fluid flow tosaid hydraulic motor thereby controlling the direction of rotation ofsaid output shaft, said first and second valve means beinginterconnected for simultaneous operation whereby said output shaft willbe caused to rotate in one direction upon actuation of said first clutchmeans and in the opposite direction upon actuation of said second clutchmeans. l I i =1

1. A hydraulic motorized wheel for use as a drive wheel of a vehicle,said motorized wheel comprising a housing adapted to be mounted on avehicle, a casing rotatably mounted relative to said housing, ahydraulically operated motor mounted on said housing having a rotatabledrive shaft extending into said casing, a planetary gear set in saidcasing, the sun gear of said planetary gear set being driven by saiddrive shaft, said planetary gear set further including a planetary geardisposed in driving engagement with said sun gear, a planetary gearcarrier mounted in said casing for relative sliding movement in eitherdirection from a neutral position, said planetary carrier being freelyrotatable relative to both said casing and said housing when in saidneutral position, and a ring gear mounted in said casing in drivingengagement with said planetary gear, first clutch means in saidmotorized wheel operable upon actuation thereof to move said planetarycarrier in one direction from said neutral position to prevent relativerotation between said housing and said planetary carrier and to providea first drive ratio, and second clutch means in said motorized wheeloperable upon actuation thereof to move said planetary carrier in theother direction from said neutral position to prevent relative rotationbetween said casing and said planetary carrier to provide a second driveratio.
 2. The invention of claim 1 wherein said first and second clutchmeans are selectively actuatable by hydraulic pressure, and valve meansin fluid communication with said hydraulic motor and both of said clutchmeans, said valve means being operable to reverse the direction ofoperating fluid flow to said hydraulic motor simultaneously withactuation of said second clutch means after actuation of said firstclutch means to reverse rotation of sAid output shaft simultaneouslywith actuation of said second clutch means.
 3. The invention of claim 1wherein said hydraulic motor includes an externally toothed member, aninternally toothed member, and motor valve means, said externallytoothed member being operably associated with said drive shaft andeccentrically disposed relative to said internally toothed member forrotational and orbital movement relative to an axis thereof, the teethof said members intermeshing to define expanding and contracting fluidchambers upon relative rotational and orbital movement therebetween,said motor valve means being connected to admit and exhaust fluid fromsaid chambers in synchronism with one of the movements of saidexternally toothed member.
 4. The invention of claim 3 wherein the driveshaft of said hydraulic motor includes splined portions thereon, andsaid externally toothed member has a splined bore therein, one of saidsplined portions of said drive shaft being drivingly received in thesplined bore of said externally toothed member, another of said splinedportions being the sun gear for said planetary gear set.
 5. A hydraulicmotorized wheel for use as a drive wheel vehicle, said motorized wheelcomprising a housing adapted to be mounted on a vehicle, a casingrotatably mounted relative to said housing, a hydraulically operatedmotor mounted on said housing having a rotatable drive shaft extendinginto said casing, a planetary gear set in said casing, the sun gear ofsaid planetary gear set being driven by said drive shaft, said planetarygear set further including a planetary gear disposed in drivingengagement with said sun gear, a planetary gear carrier mounted in saidcasing for normally free rotation relative to both said casing and saidhousing, and a ring gear mounted in said casing in driving engagementwith said planetary gear, said planetary gear carrier being axiallyslidable relative to said ring and sun gear in either direction from aninitial neutral position where said planetary carrier is freelyrotatable relative to both said casing and said housing, first clutchmeans in said motorized wheel operable upon actuation thereof to preventrelative rotation between said housing and said planetary carrier and toprovide a first drive ratio, said first clutch means including pressureactuatable means for moving said carrier in one direction from saidneutral position, second clutch means in said motorized wheel operableupon actuation thereof to prevent relative rotation between said casingand said planetary carrier to provide a second drive ratio, said secondclutch means including pressure actuatable means for moving said carrierin the other direction from said initial neutral position, and meansnormally biasing said carrier toward said initial neutral position. 6.The invention of claim 5 wherein said first and second clutch meanscomprise first and second clutching surfaces on said carrier andcorresponding adjacent clutching surfaces on said housing and saidcasing respectively.
 7. The invention of claim 6 wherein a first elementof clutch frictional material is disposed between the first clutchingsurface on said carrier and the corresponding surface on said housing,and a second element of clutch frictional material is disposed betweenthe second clutching surface on said carrier and the correspondingsurface on said casing.
 8. The invention of claim 7 wherein said firstclutch means includes a first piston received in a recess in saidcasing, said first piston having a bearing surface disposed for abuttingengagement with a bearing surface of said carrier, said second clutchmeans including a second piston received in a recess in said housing,said second piston having a bearing surface disposed for abuttingengagement with a bearing surface of said carrier, and wherein thebiasing means for normally biasing said carrier toward said initialneutral position comprise biasing means acting between saId casing andsaid first piston and said housing and said second piston to constantlyurge said surfaces toward abutting engagement and to thereby urge saidcarrier toward the initial neutral position.
 9. The invention of claim 5wherein said first and second pressure actuatable means comprise annularpistons received in recesses in said casing and said housingrespectively on opposite sides of said carrier and selectivelypressurizable passage means in said casing and said housingcommunicating with said recesses.
 10. The invention of claim 9 whereinsaid means normally biasing said carrier toward said initial neutralposition comprise springs acting between the casing and its associatedpiston and the housing and its associated piston thereby biasing saidpistons into engagement with said carrier and thereby biasing saidcarrier toward said initial neutral position.
 11. A hydraulic motorizedwheel for use in a vehicle, said motorized wheel comprising a housingadapted to be mounted on a vehicle, a casing mounted on said housing forrotation relative thereto, a reversible rotary hydraulic motor disposedon said housing and having rotatable output shaft extending into saidcasing, a planetary gear set disposed in said casing, said planetarygear set including a sun gear, planetary gears, planetary gear carriermeans and a ring gear, the sun gear of said planetary gear set beingdrivingly connected for rotation with the output shaft of said hydraulicmotor, first clutch means operable upon actuation thereof to preventrotation of said casing relative to said sun gear to thereby provide afirst drive ratio between said output shaft and said casing, secondclutch means operable upon actuation thereof to prevent rotation ofanother portion of said planetary gear set relative to said housing tothereby provide a second driving ratio between said output shaft andsaid casing, a first valve in fluid communication with said motorizedwheel, said first valve being operable to selectively actuate said firstand second clutch means, and a second valve in fluid communication withsaid motorized wheel, said second valve being operable to control thedirection of operating fluid flow to said hydraulic motor therebycontrolling the direction of rotation of said output shaft, said firstand second valve means being interconnected for simultaneous operationwhereby said output shaft will be caused to rotate in one direction uponactuation of said first clutch means and in the opposite direction uponactuation of said second clutch means.